The paper pick mechanism of the kind shown in U.S. Pat. No. 5,527,026 to Padget et al. employs a drive roller on a pivoted arm and excess paper height is unacceptable as the device requires at least a predetermined downward angle of the arm for reliable functioning. When the stack is too high, drive rollers tend to slip on the top sheet rather than move it. Accordingly, the paper stack height must be controlled.
Additionally, the preferred implementation of the paper tray employs a sloped, smooth surface, termed a dam, as the initial surface against which the paper is moved by the drive rollers. The dam-style paper tray is essentially a box into which the paper or other media is dropped. There is no physical element, such as the commonly used buckling ledge (termed a corner buckler), under which the media must be positioned.
With the absence of a corner buckler, no physical stack limiter is present in the paper tray itself. Typically, a label is placed on the side of the tray to show maximum stack height, and the user must voluntarily comply with the indication on the label. Accordingly, filling the tray above the defined point is easy and might frequently occur, which would contribute to paper feed failures.